Indicator: Grassland butterfly index
Indicator name

Tag: SDG_15_61
Indicator abbreviated name

Definition: The indicator is an index measuring changes in population abundance at EU level of 15 grassland butterfly species, using 1991 as the reference year.
Definition describing what the indicator measures

Unit: Index measuring changes in population abundances of butterfly species compared to the reference year 1991 (Index 1991 = 100).
Measurement unit of the indicator values

Spatial coverage: EU (continental territories only; country composition varies by reporting year)
Geographic area covered by the indicator

Temporal coverage: 1991-2024
Time coverage of the indicator from first to most recent available year

Update frequency: Every year
Frequency at which indicator is updated

DPSIR: State
DPSIR classification framework: Driver, Pressure, State, Impact, or Response

Method: 1) Calculation of scheme-level indices per each species; 2) calculation of a collated index for EU27 for each species by fitting a Poisson GLM; 3) calculation of the EU27 indicator by taking the geometric mean of the single-species indices; 4) calculation of a smoothed indicator using a loess smooth with span=0,75 and degree=2. More information can be found in Van Swaay et al., 2020. Assessing Butterflies in Europe - Butterfly Indicators 1990-2018 Technical report. Butterfly Conservation Europe & ABLE/eBMS; and on the website of the European Butterfly Monitoring Scheme: https://butterfly-monitoring.net/bms-methods.
Description of the main methodological steps used to calculate the indicator

Reference: Sustainable development in the European Union - Monitoring report on progress towards the SDGs in an EU context - 2025 edition (https://ec.europa.eu/eurostat/web/products-flagship-publications/w/KS-01-24-018), accessed 24 February 2026. van Swaay, C. A. M., Nowicki, P., Settele, J. and van Strien, A. J., 2008, 'Butterfly monitoring in Europe: methods, applications and perspective', Biodiversity and conservation 17(14), pp. 3455-3469. van Swaay, C. A. M., Dennis, E. B., Schmucki, R., Sevilleja, C. G., Aghababyan, K., Åström, S., Balalaikins, M., Bonelli, S., Botham, M., Bourn, N., Brereton, T., Cancela, J. P., Carlisle, B., Chambers, P., Collins, S., Dopagne, C., Dziekanska, I., Escobés, R., Faltynek Fric, Z. et al., 2020, Assessing Butterflies in Europe - Butterfly Indicators 1990-2018: Technical report, Butterfly Conservation Europe & ABLE/eBMS (www.butterfly-monitoring.net), accessed 24 February 2026.
Reference sources describing the indicator and method to calculate it (e.g. peer-reviewed articles, scientific/technical reports, webpages, other)

Producer: European Butterfly Monitoring Scheme partnership
Institution which produces the calculation of the indicator values

Provider: Eurostat
Institution supplying the indicator values, even if not the original producer of indicator values

Open source: False
Indicates whether calculation code is openly available

Spatial scope (Member States): False
Whether the indicator is available at Member States level

Spatial scope (EU27): True
Whether the indicator is available at EU27 aggregated level

Spatial scope (global): False
Whether the indicator is available at global level

Accuracy uncertainties: Not assessed
Comment on data accuracy, limitations, and uncertainty

Comments: None
Additional remarks

Storage: None
Webpage link containing the code and/or detailed description of the workflow to calculate the indicator

Copyright/Licence of use: Eurostat copyright notice: https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Copyright/licence_policy.
Copyright or licensing information related to the indicator